Embodiments of the inventive subject matter generally relate to the field of network transmissions, and, more particularly, to adjusting carrier modulation and carrier transmission power in multi-carrier transmissions.
Communication technology is evolving to allow for better channel estimation and adaptation of transmissions over a communication channel. For example, in many technologies, such as powerline communications, a medium between a first device and a second device may support multi-carrier transmissions. Other medium and technologies may also use multi-carrier transmissions in which multiple frequencies are used over a communication channel. Indicators that may be used as a measurement of the quality of a transmission via a signal (e.g. via a frequency) include the signal-to-noise ratio (SNR) or signal-to-interference-plus-noise (SINR).
The formula for SINR may be defined as P/(I+N) where P represents the received power, I represents the interference power of other simultaneous transmissions, and N represents the noise (such as background or intermittent noise). Often, “noise” will be defined to include interference as well as background noise or intermittent noise. Therefore, when measuring signal to noise ratio, the measurement may be referred to as SNR or SINR interchangeably in some systems.
SNR is used as a measurement of the quality of a transmission via a signal because it correlates closely with a receiver's ability to interpret the transmitted signal. In traditional systems, SNR may also correlate with a power level of a transmitted signal. When a power level of a transmitted signal is high the SNR high, and conversely when a power level of a transmitted signal is low the SNR is low.